OMG, I love your ideas behind his interactions with the villains, especially the likes of LRW, Ms. Question, and Kid Potato. Though you know, I could see him weirdly getting along better with the likes of Tibet and Becky more then Becky could. And of course, because he tends to be so logical, I could see him getting along with some of the few villains that have brain cells such as Leslie and Reason.
[Contains WordGirl finale spoilers for "Rhyme and Reason" episode, letting my followers know in case there's anyone who started watching after I started posting WG]
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Yeah, I definitely see Rex getting along great with Tobey and that's one of the arcs we'll get to see in my new Factor It In 'fic, actually! Tobey thinks about WordGirl and Kid Math a lot, especially since his bedroom window is in a great position to see them zooming back and forth across the city.
Tobey and Rex both have scientific minds. Tobey likes to research and experiment, and Rex likes to volunteer for adventures 🙂
Honestly I've never given any thought to Rex and Reason meeting (My unpopular opinion is that Rhyme and Reason bounced on to another city after getting out of jail since they've always been on the move and there's no reason to stick around a superhero they lost a fight to when they're not emotionally attached to this place that hurt them anyway... either that, or they quit being villains after getting out of jail because they finally hit a wall they couldn't climb so they just sort of unwound and sprawled on the emotional floor to evaluate their relationship and talk about feelings and then Rhyme let Reason decide which direction to steer their lives... I'm not sure yet!)
I think my headcanons for Rex and Reason would be... Reason is the more controlled, rational version of Rex by FAR. He's an adult and Rex is an unhinged child masquerading as a rational person. My personal "28 Cities" take on Reason was that he grew up in a stable apartment. He's the "regular guy." The comedic straight man.
Reason kind of goes about his day and he plays the foil to Rhyme, but he doesn't make his villain identity his persona to the degree that Rhyme takes hers. I like to think of him as just following in her footsteps, letting her call the shots while his job is to make sure HER plans go the right direction, and that's why their break-up in "Rhyme and Reason" was so explosive. Reason was finally standing up for himself and explaining that he was uncomfortable with their villain lifestyle.
Anyway, Reason is an adult who like, wants to own houseplants and decorate his home office and cook nice food in a nice apartment with his best friend. He does the villain thing mostly because Rhyme likes it, but he doesn't contribute much to it except emotional support, like the big teddy bear he is. The way I see it, Reason is the "functional logical." Completely plain. He budgets. Does his meal planning. Sets aside time for laundry day. Washes his bedsheets once a week.
I see Reason as "average joe who just happens to be best friends with a girl with powers." He's basically a civilian. Rex, however, is a child genius raised in a classroom of child geniuses. He got accepted into the superhero training program and he's extremely proud of his education. His hero complex is insane.
Rex has superpowers that are constantly filling his head with calculations. He lives in a constant state of knowing exactly what time it is, knowing his exact latitude and longitude, identifying people's heights and weights, recognizing the temperature, converting between metric and customary systems and many others, making calendar conversions, etc.
Rex can thumb through the ingredients in a sandwich and, because of superpowers, inherently recognize how many calories he'll gain and how many calories he'll burn from performing certain actions. His powers are number-based, so he can't ask himself "What action should I take?" and have an action pop into his head, but he can look at a person standing in front of him and his brain will instantly supply him with the info about their height, weight, mass, and how many calories he'll burn while punching them.
Rex naturally perceives himself as logical because he attended a school program that was specifically for training Hexagonian heroes. I've seen a lot of takes on WordGirl lore where all Lexiconians and Hexagonians have powers while on their planet, but my personal take on the lore is "You only get powers after you leave the planet." This means in my headcanon, Rex was a regular schoolkid learning all the science about flying, and being told that one day he would have calculations popping into his head, but he had to get through all his schooling without his powers.
It wasn't until he was off the planet that he started flying for the first time, so he really is just bumbling around Earth and trying to adjust to his powers for the first time (hence why I portray him with sensory overload so much-- it's very new to him). This makes him incredibly unhinged and dangerous because he has all the knowledge of what a hero should be doing, and he knows a lot of facts about his abilities, but he has no practical experience and no control (while WordGirl has all the control but lacks the official superhero training, she's mostly self-taught with a bit of advice from mentors), slkdfj.
Anyway, Rex takes actions he perceives as logical because he's constantly being fed calculations. Those are observations he can't turn off. Reason's just Some Guy. I think they might discover they have a few things in common, like a love for healthy snacks, but Rex wouldn't clock Reason as a threat and would redirect his energy to Rhyme... Reason can just be picked up and put on a roof and then he's out of the fight, slkdfj.
I'm not sure what they'd actually talk about. Rex isn't the chatty type, although he does love to brag. He'd probably boast about all the fantastic math he can do and Reason would finally get fed up and challenge him to a math problem-solving race. Reason definitely doesn't have the Hexagonian auto-calculator in his brain that Rex does, but he likes math enough to make his logo a square root sign, so he probably likes it enough that he can keep up with Rex a little bit during discussions.
I think Rex would effortlessly obliterate Reason with math knowledge and be accidentally condescending about it because he's oblivious, and it would upset Reason a lot because he's the guy without powers and He Gets One Nice Thing In This Villain Business and it's being seen as the smart and logical guy... and Rex takes that away from him. Reason is this incredibly beautiful blend of "Short fuse before he snaps" before he gets control of himself and veers into "Patience of a saint." He'd be loud and upset for a second, then cool off by the time Rex turns around and he'd just simmer in his own anger...
Those are some of my thoughts! Thanks for being interested in my headcanons <3